1. Field of the Invention
The present invention relates generally to scanners and scanning methods, and more particularly to a duplexing auto-document feeder (ADF) using a paper path shorter than the length of paper to be duplexed.
2. Description of the Related Art
All-in-one machines typically perform functions such as printing, scanning, copying, and faxing in either a stand alone fashion or in conjunction with a personal computer and define a growing market for peripheral devices. These devices eliminate clutter in a business or home office by combining the desirable functionality of various machines into a single unit, while maintaining an affordable cost. Various all-in-one machines currently in the marketplace use thermal inkjet technology as a means for printing received fax documents, original documents, and copied or scanned images or text. Thermal inkjet printing devices utilize consumable inkjet cartridges in fluid communication with a printhead to record text and images on a print media. The printhead typically moves on a carriage relative to the media path and a control system activates the printhead to selectively eject ink droplets onto the print media.
Scanners are used to scan a target image and create scanned image data which can be displayed on a computer monitor, which can be used by a computer program, which can be printed, which can be faxed, etc. Scanned data may be saved to memory or a magnetic or optical drive, or other fixed or removable memory device. Scanning devices may be packaged in a stand-alone housing or as part of the all-in-one device, as described herein, including a printing module to perform scanning as well as standard copying functions.
Scanners typically include a housing aperture defined by an edge wherein a platen is located. A target document is positioned on the platen for scanning of the text or image by a scanbar. Depending on the positioning of the scanbar relative to the platen, the platen may be transparent where the scanbar is beneath the platen or may be solid where the scanbar is above the platen. For a typical flatbed scanner, the scanbar will be below the platen, which will have a transparent section to allow for the scan operation.
The scanner may also include an auto-document feeder (ADF) to automatically and sequentially feed a plurality of documents to a scan module. The automatic document feeder typically comprises a feed tray and an input device which feeds a single sheet from the stack of media on the feed tray into the automatic document feeder media path. The single sheet of media passes the reading position where the media is illuminated and image data is created by the scanbar representing images on the media. The media then passes from the auto-document feeder to a stacking tray where the media remains until all of the media from the feed tray has been scanned and is removed from the stacking tray at the output side of the auto-document feeder.
Generally most auto-document feeders are single-side imaging devices. To scan a double-sided image, the media must be turned which is often done manually. Prior art patent have taught various means for reversing media sides and performing double-sided or duplex scanning. According to one method of duplex scanning, the scanning module comprises first and second image sensors to scan first and second sides of the media. However, the problem with these devices is that the two image sensors require large amounts of space and therefore make the equipment footprint much larger. This is not suitable for many applications, such as home, office equipment or small office equipment and further increases the costs of the device which is also undesirable.
While it may be desirable to decrease the footprint of a duplexing auto-document feeder, the shortening the feedpath leads to problems such as overlapping media edges. When media overlaps in a nip, media feed becomes inconsistent leading to decreased scan quality.
Given the foregoing deficiencies, it will be appreciated that an improved apparatus for creating a duplex scan is needed.